Mercury switch



Nov. 17,1931. P. K. CRAMBLET MERCURY SWITCH Filed Dec. 7, 1928gru/vento@ novel pio Patented Nov. '/17, 1931 UNITED STATES PATENTOFFICE PAUL K. CRAMBLET, OFMILWAUKIEE, WISCONSIN, ASSIG-NOR, BY MESN EASSIGNMENTS',

'ro mINNnAroLIs-HONEYWELL sore, A ooarom'rron or' DELAWARE REGULATORCOMPANY, OFY MINNEAPOLIS, MINNE- MERCURY SWITCH Application filedDecember 7, 1928. -Serial No.. 324,494.

l This invention relates in general to mercury switches and moreparticularly to a protective casing land mounting for mercury switchesand to a method of making 'the same.

Mercury switches usually have an outer envelope of soft glass which isadvantageous in that it is com aratively inexpensive and easily worked.ther materials have been proposed and in some instances used but theyare either too expensive or too dillcult to work or else have some otherserious disadvantage. The sole disadvantage of the soft glass outerenvelope so widely employed is its frangibility, as a result of which itis liable to and frequently does become broken or cracked when subjectedto the usage of ac; tual practice. If the envelope of the switch becomescrackedorpbroken its operativeness is at once impaired not only becauseof the loss of the mechanical strength and structure of the outerenvelope but also because the atmosphere of hydrogen or other inert gasessential to efficient -switch operation is lost, and, if the crackbecomes pronounced, there is loss of the mercury.

The present invention y sion of a protective' casing or covering for thevor resilient so as to outer envelope of the switch which is elasticabsorb and distribute shocks or strains whichwould ordinarily be appliedto the envelope and concentrated'upon a small portion thereof and resultin cracking or breaking Further, is impervious to the air or gas and soit hermetically seals the mercury switch within it.

As a consequence even though the envelope cracked the protectivecasingmaintains the structural integrity and mechanical strength of the switchand prevents loss of the possible to proposes the provithe covering tothe glass envelope being distributed over the entire area thereof.

Another object of the invention is to provide a protective coveringhaving these advantages and capacities and which makes it provide amercury switch with completely sealed and insulated supply conductors,whereby the mercury switch may be immersed and operated in a fluid andcompletely protected and insulated therefrom.

Other objects and advantages reside in certain novel features'of theconstruction, arrangement -and combination of parts which will behereinafter more fully described and particularly pointed out in theappended claims, reference being had to the accompanying drawings,specification, and in which:

Figure 1 is a view in central longitudinal vertical cross sectionshowing a mercury switch equipped with a protective covering embodyingthe present invention;

Figure 2' is a view thereof in cross section taken on line 2 2 of Figure1;

Figure 3 is a view similar to Figure 1 but showing another form of theinvention;

Figure 4 is a view in cross section taken on line 4--4 of Figure 3;

Figure 5 is a view in side elevation illustrating one mode of mountingand operating the switch; and

Figure 6 is a sectional view taken in they plane of line 4 4 of Figure3' and illustrating how this switch construction can be organlzed withcompletely insulated supply conductors. y

Referring to the drawings, and more particularly to Figures 1 and 2, thenumeral 1 designates generally a mercury switch which may be of anysuitable construction. The particular switch shown is selected merelyfor the purposes of illustration and, of course, any type of mercurswitch may be utilized. For example, switc es ofthe type having a.mercury to mercury make and reak may be utilized. As illustrated, themercury switch has an outer glass envelope 2 containing a body ofmercury 3 and an atmosphere of inert gas. Electrodes 4 and 5 are sealedin through the envelope 2 and as the switch forming a part of this 4 and5 by this switch operation.

is operated the mercury alternately makes and breaks the circuit acrossthe electrodes bridging these electrodes in one position of the switchand by flowingaway from and out of `contact with the electrode 5 in theother position of the switch.`

The present invention proposes to enclose.

and seal the outer envelope 2 1n a covering or casing of rubber,designated at 6, the rubber completely surrounding the envelope and alsoportions at least of the electrodes 4 and 5 which lead thereinto.

In the form of the invention shown in Figure 3, a mercury switch isdesignated generally at 10 and has an outer soft glass envelope 11through which electrodes 12 and 13 are sealed. The switch also containsa body of mercury 14 which operates to make and break thel electricalcircuit whenv the switch is operated. The particular manner in which themercury accomplishes this is immaterial to the present invention, as thepresent invention is applicable to all thevarious methods and structuresthat have been proposed in mercury switches for effecting As isconventional, the envelope contains an atmosphere of inert gas, such ashydrogen, which suppresses arcing.

As in the embodiment of the invention rst described, the envelope 10 isenclosed or embedded in a covering or casing of rubber designated at 15.In this form of the invention the portions of the electrode 12 and 13projecting outside of the envelope 11 and the exible'leads 16 and 17connected thereto, are all completely and entirely embedded in the bodyof the rubber covering 15. At the opposite sides of its center, therubber casing 15 is provided with integral laterally extending mountinglugsv 18, having centrally located apertures 19 lined with flangedbushings 20 of material that is a good conductor of electricity. Theleads 16 and 17 are electrically connected with these bushings 20 andthe external circuit is connected to the bushings 20 inany suitablemanner.

The lugs 18 are adapted to co-act with any appropriate form of mounting.In Figure 5 an illustrative example of the mounting is shown at 25 andthe lugs are secured to this mounting in any suitable manner as by meansof nuts 25 threaded on the mounting and clamping the lugs 18 betweenthem. This enables the switch to be oscillated by alternately exertingpressure upon one end of the switch and relieving it` of such pressure.Thus, as shown in Figure 5, an operating arm 26 fixed on a rocking oroscillating shaft 26 may be provided to periodically press down on oneend of the switch thereby tilting the switch due to the flexion of itslugs 18. The inherent elasticity of the lugs 18 returns the switchautomatically to its normal position as soon as the pressure exerted bythe arm 26 is relieved.

As will be understood from the foregoing and from a consideration ofFigures 4 and 5, this'construction avoids all exposed leads and it maybe readily adapted toa construction which is associated with completelyinsulated lead-in supply conductors. Thus, as shown in Figure 6, acombined mounting and supply conductor designated generally at 27 isprovided for each mounting lug and is encased in an insulating cover 28except for the portion thereof that projects into the bushing 20 andengages the nuts 25. The exposed portions of the bushings 20, nuts 25and combined mountings and supply conductors 27 are covered by applyinggum rubber thereto as indicated at 29 after the assembly has beencompleted.

The rubber covering or casing may be ap plied to the mercury switch ineither of the foregoing embodiments in various ways which are well knownto those skilled in the art of rubber. But a highly effective andpreferred method of producing a protected switch of this character is totake the completely constructed conventional mercury switch and firstdip it into gum rubber and then allow it to set.- Several clippings anddryings may be resorted to, if desired, but usually one is suicient.After the dipping in gum rubber the coated tube is placed in a soapedmold. The mold is then closed and a plastic rubber compound is forcedinto the mold to compleiely surround the coated mercury switch and theportions of its electrodes or all of its electrodes, as desired.Finally, the assembly is subjected to heat to cure the rubber and effectvulcanization.

Another method is to take the tube after it has been coated with the gumrubber and place it on a sheet of soft plastic rubber contained in onesection of the mold. Another sheet of similar rubber is placed in theother section of the mold and then the mold scctions are broughttogether to cause the sheets to encompass the switch and to squeeze outthe excess of rubber. With the mold sections secured -together theassembly is subjected to heat to effect curing and vulcanizing of therubber. Either of these methods may be practiced without the priordipping in the gum rubber but the dipping in the gum rubber while notessential for all purposes is preferable as it greatly increases theimperviousness of the protective casing to air and gas and makes itpossible for the switch to stand up over a long period of time even ifthe glass envelope thereof has been cracked.

It is to be understood that while one form of mounting means is shown,various forms may be utilized. The structure shown in Figure 1 isparticularly adapted for use with mountings employing resilient clips orgrippers. Any form of mounting that is utilized may firmly grip theswitch and yet the gripping pressure is distributed over the whole tubethrough the elastic casing.

Vhere a mounting of the type shown in Figure 2 is employed the mountingtakes part in the operation of the switch, as above pointed out, for theinherent resiliency of the lugs automatically return the switch tor`normal position after each positive actuation thereof by the operatingmeans. Further, the protective casing protects the tube against breakageby distributing or absorbing shocks or stralns. Finally, as pointed out,even in the event of breakage of the outer envelope the protectivecasing preserves the mechanical strength and structure of the switch andprevents loss of its arc suppressing gas or loss of its mercury.

While the covering or casing is preferably constituted of rubber, it isobvious that it may be made up of any suitable material having therequisite elasticity and the property of being impervious to air andgas.

The invention claimed is:

1. In combination, a mercury switch having electrodes, fiexible leadsconnected to the electrodes of the switch, and a covering of, elasticrubber completely surrounding the switch, the electrodes and the leadsto protect and hermetically seal the same, said covering having integralmounting lugs.

2. In combination, a mercury switch, iiexf ible leads connected to theelectrodes of the switch, and a covering of elastic rubber completelysurrounding the switch, the electrodes and the leads to protect andhermetically seal the same, said covering having integral mounting lugs,said mounting lugs having electrical connectors embedded therein andconnected to the flexibleleads.

3. In combination, a mercury switch and Aan elastic rubber coveringcompletel encasing the switch and hermetically sea ing the same andhaving integral mounting means adapted to co-act with the mounting tosupport the switch and to bias the same to a normal position.

4. In combination, a mercury switch and an elastic covering completelencasing the switch and hermetically sea ing the same, and havingintegral lugs formed with bushed openings adapted to co-act withsupporting means and electrical supply conductors.

5. In combination, a mercury switch and an elastic covering completelyencasing the switch and hermeticallysealin the same, and having integrallugs forme with bushed openings adapted to co-act with supporting meansand electrical supply conductors, and flexible leads embedded in thecovering and extending from the bushings to the electrodes of theswitch.

6. In combination, a mercury switch having an outer glass envelope andelectrodes sealed therethrough, an elastic covering com- 65 pletelyencasing the switch and hermetically 'elastic covering therefor havingelastic mounting members supporting the switch and biasing the same toone position, and means for periodically displacing the switch -toanother position against the biasing action of the mounting members.

In witness whereof, I hereto afiiX my signature.

PAUL K. CRAMBLET.

